Gamma-ray Burst 200425A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

 
TITLE:           GCN/SWIFT NOTICE 
NOTICE_DATE:     Sat 25 Apr 20 00:17:11 UT 
NOTICE_TYPE:     Swift-BAT GRB Position 
TRIGGER_NUM:     967774,   Seg_Num: 0 
GRB_RA:           85.241d {+05h 40m 58s} (J2000), 
                  85.474d {+05h 41m 54s} (current), 
                  84.667d {+05h 38m 40s} (1950) 
GRB_DEC:         -13.459d {-13d 27' 31"} (J2000), 
                 -13.450d {-13d 26' 58"} (current), 
                 -13.483d {-13d 28' 59"} (1950) 
GRB_ERROR:       3.00 [arcmin radius, statistical only] 
GRB_INTEN:       10538 [cnts]    Image_Peak=344 [image_cnts] 
TRIGGER_DUR:     4.096 [sec]  
TRIGGER_INDEX:   298     E_range: 25-100 keV 
BKG_INTEN:       88756 [cnts] 
BKG_TIME:        927.17 SOD {00:15:27.17} UT 
BKG_DUR:         40 [sec] 
GRB_DATE:        18964 TJD;   116 DOY;   20/04/25 
GRB_TIME:        981.76 SOD {00:16:21.76} UT 
GRB_PHI:          -4.50 [deg] 
GRB_THETA:        12.68 [deg] 
SOLN_STATUS:     0x3 
RATE_SIGNIF:     13.49 [sigma] 
IMAGE_SIGNIF:    8.62 [sigma] 
MERIT_PARAMS:     +1  +0  +0  +2  +2  -1  +0  +0 -52  +0  
SUN_POSTN:        32.98d {+02h 11m 54s}  +13.28d {+13d 16' 33"} 
SUN_DIST:         58.48 [deg]   Sun_angle= -3.5 [hr] (East of Sun) 
MOON_POSTN:       54.85d {+03h 39m 24s}  +16.57d {+16d 34' 10"} 
MOON_DIST:        42.62 [deg] 
MOON_ILLUM:      3 [%] 
GAL_COORDS:      217.43,-21.60 [deg] galactic lon,lat of the burst (or transient) 
ECL_COORDS:       84.22,-36.80 [deg] ecliptic lon,lat of the burst (or transient) 
COMMENTS:        SWIFT-BAT GRB Coordinates.   
COMMENTS:        This is a rate trigger.   
COMMENTS:        A point_source was found.   
COMMENTS:        This does not match any source in the on-board catalog.   
COMMENTS:        This does not match any source in the ground catalog.   
COMMENTS:        This is a GRB.   
COMMENTS:        This trigger occurred at longitude,latitude = 253.26,19.68 [deg].

red DSS finding chart ps-file

GCN NOTICE

 
TITLE:           GCN/SWIFT NOTICE 
NOTICE_DATE:     Sat 25 Apr 20 00:18:07 UT 
NOTICE_TYPE:     Swift-XRT Nack-Position 
TRIGGER_NUM:     967774,   Seg_Num: 0 
POINT_RA:         85.237d {+05h 40m 57s} (J2000) 
POINT_DEC:       -13.465d {-13d 27' 52"} (J2000) 
IMG_START_DATE:  18964 TJD;   116 DOY;   20/04/25 
IMG_START_TIME:  1072.28 SOD {00:17:52.28} UT,   90.5 [sec] since BAT Trigger Time 
COUNTS:          44    Min_needed= 20 
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec] 
PH2_ITER:        4    Max_iter_allowed= 4 
ERROR_CODE:      2 
COMMENTS:        SWIFT-XRT Nack Position.   
COMMENTS:        Algorithm did not converge; too many iterations.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Apr 20 00:22:06 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     967774,   Seg_Num: 0
GRB_RA:           85.241d {+05h 40m 58s} (J2000),
                  85.474d {+05h 41m 54s} (current),
                  84.667d {+05h 38m 40s} (1950)
GRB_DEC:         -13.459d {-13d 27' 31"} (J2000),
                 -13.450d {-13d 26' 58"} (current),
                 -13.483d {-13d 28' 59"} (1950)
GRB_DATE:        18964 TJD;   116 DOY;   20/04/25
GRB_TIME:        981.76 SOD {00:16:21.76} UT
TRIGGER_INDEX:   298
GRB_PHI:          -4.50 [deg]
GRB_THETA:        12.68 [deg]
DELTA_TIME:      16657.00 [sec]
TRIGGER_DUR:     4.096 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     13.49 [sigma]
IMAGE_SIGNIF:    8.62 [sigma]
LC_URL:          sw00967774000msb.lc
SUN_POSTN:        32.98d {+02h 11m 55s}  +13.28d {+13d 16' 37"}
SUN_DIST:         58.47 [deg]   Sun_angle= -3.5 [hr] (East of Sun)
MOON_POSTN:       54.89d {+03h 39m 34s}  +16.58d {+16d 34' 55"}
MOON_DIST:        42.60 [deg]
MOON_ILLUM:      3 [%]
GAL_COORDS:      217.43,-21.60 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       84.22,-36.80 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:           
COMMENTS:        The next comments were copied from the BAT_POS Notice:  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 253.26,19.68 [deg].  
COMMENTS:        The 3rd packet (of 3) was missing in the lightcurve data stream.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Apr 20 00:32:01 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     967774,   Seg_Num: 0
POINT_RA:         85.237d {+05h 40m 57s} (J2000)
POINT_DEC:       -13.465d {-13d 27' 52"} (J2000)
POINT_ROLL:      295.192d
IMG_START_DATE:  18964 TJD;   116 DOY;   20/04/25
IMG_START_TIME:  1075.48 SOD {00:17:55.48} UT,   93.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.169
N_STARS:         54
X_OFFSET:        504 [pixels]
Y_OFFSET:        624 [pixels]
X_MAX:           1463 [pixels]
Y_MAX:           1583 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00967774000msufc0093.fits
SUN_POSTN:        32.99d {+02h 11m 57s}  +13.28d {+13d 16' 45"}
SUN_DIST:         58.47 [deg]   Sun_angle= -3.5 [hr] (East of Sun)
MOON_POSTN:       54.97d {+03h 39m 54s}  +16.61d {+16d 36' 25"}
MOON_DIST:        42.56 [deg]
MOON_ILLUM:      3 [%]
GAL_COORDS:      217.43,-21.61 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       84.21,-36.81 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Apr 20 00:33:16 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     967774,   Seg_Num: 0
POINT_RA:         85.237d {+05h 40m 57s} (J2000)
POINT_DEC:       -13.465d {-13d 27' 52"} (J2000)
ROLL:            295.192d
IMG_START_DATE:  18964 TJD;   116 DOY;   20/04/25
IMG_START_TIME:  1075.48 SOD {00:17:55.48} UT,   93.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     609466700
X_OFFSET:        823 [pixels]
Y_OFFSET:        943 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       983
Y_GRB_POS:       1103
BINNING_INDEX:   1
IM_URL:          sw00967774000msuni0118.fits
SUN_POSTN:        32.99d {+02h 11m 57s}  +13.28d {+13d 16' 46"}
SUN_DIST:         58.47 [deg]   Sun_angle= -3.5 [hr] (East of Sun)
MOON_POSTN:       54.98d {+03h 39m 56s}  +16.61d {+16d 36' 37"}
MOON_DIST:        42.56 [deg]
MOON_ILLUM:      3 [%]
GAL_COORDS:      217.43,-21.61 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       84.21,-36.81 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Apr 20 00:33:30 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     967774,   Seg_Num: 0
POINT_RA:         85.237d {+05h 40m 57s} (J2000)
POINT_DEC:       -13.465d {-13d 27' 52"} (J2000)
ROLL:            295.192d
IMG_START_DATE:  18964 TJD;   116 DOY;   20/04/25
IMG_START_TIME:  1075.48 SOD {00:17:55.48} UT,   93.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     609466700
X_OFFSET:        823 [pixels]
Y_OFFSET:        943 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       983
Y_GRB_POS:       1103
BINNING_INDEX:   1
IM_URL:          sw00967774000msuni0118.fits
SUN_POSTN:        32.99d {+02h 11m 57s}  +13.28d {+13d 16' 46"}
SUN_DIST:         58.47 [deg]   Sun_angle= -3.5 [hr] (East of Sun)
MOON_POSTN:       54.99d {+03h 39m 57s}  +16.61d {+16d 36' 39"}
MOON_DIST:        42.56 [deg]
MOON_ILLUM:      3 [%]
GAL_COORDS:      217.43,-21.61 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       84.21,-36.81 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Apr 20 00:34:34 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     967774,   Seg_Num: 0
GRB_RA:           85.2203d {+05h 40m 52.87s} (J2000),
                  85.4537d {+05h 41m 48.87s} (current),
                  84.6461d {+05h 38m 35.06s} (1950)
GRB_DEC:         -13.4343d {-13d 26' 03.4"} (J2000),
                 -13.4251d {-13d 25' 30.3"} (current),
                 -13.4589d {-13d 27' 31.9"} (1950)
GRB_ERROR:       4.4 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18964 TJD;   116 DOY;   20/04/25
IMG_START_TIME:  1222.00 SOD {00:20:22.00} UT,   240.2 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        32.99d {+02h 11m 57s}  +13.28d {+13d 16' 47"}
SUN_DIST:         58.44 [deg]   Sun_angle= -3.5 [hr] (East of Sun)
MOON_POSTN:       54.99d {+03h 39m 59s}  +16.61d {+16d 36' 48"}
MOON_DIST:        42.52 [deg]
MOON_ILLUM:      3 [%]
GAL_COORDS:      217.40,-21.61 [deg] galactic lon,lat of the burst
ECL_COORDS:       84.19,-36.78 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.11% < P(seren) < 0.58%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Apr 20 00:31:48 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     967774,   Seg_Num: 0
POINT_RA:         85.237d {+05h 40m 57s} (J2000)
POINT_DEC:       -13.465d {-13d 27' 52"} (J2000)
POINT_ROLL:      295.192d
IMG_START_DATE:  18964 TJD;   116 DOY;   20/04/25
IMG_START_TIME:  1075.48 SOD {00:17:55.48} UT,   93.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.169
N_STARS:         54
X_OFFSET:        504 [pixels]
Y_OFFSET:        624 [pixels]
X_MAX:           1463 [pixels]
Y_MAX:           1583 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw00967774000msufc0093.fits
SUN_POSTN:        32.99d {+02h 11m 57s}  +13.28d {+13d 16' 45"}
SUN_DIST:         58.47 [deg]   Sun_angle= -3.5 [hr] (East of Sun)
MOON_POSTN:       54.97d {+03h 39m 53s}  +16.61d {+16d 36' 23"}
MOON_DIST:        42.56 [deg]
MOON_ILLUM:      3 [%]
GAL_COORDS:      217.43,-21.61 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       84.21,-36.81 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Apr 20 00:38:07 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     967774,   Seg_Num: 0
POINT_RA:         85.235d {+05h 40m 56s} (J2000)
POINT_DEC:       -13.467d {-13d 28' 02"} (J2000)
POINT_ROLL:      295.192d
IMG_START_DATE:  18964 TJD;   116 DOY;   20/04/25
IMG_START_TIME:  1234.81 SOD {00:20:34.81} UT,   253.0 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.838
N_STARS:         94
X_OFFSET:        264 [pixels]
Y_OFFSET:        384 [pixels]
X_MAX:           1703 [pixels]
Y_MAX:           1823 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw00967774000msufc0253.fits
SUN_POSTN:        32.99d {+02h 11m 58s}  +13.28d {+13d 16' 50"}
SUN_DIST:         58.46 [deg]   Sun_angle= -3.5 [hr] (East of Sun)
MOON_POSTN:       55.02d {+03h 40m 06s}  +16.62d {+16d 37' 21"}
MOON_DIST:        42.54 [deg]
MOON_ILLUM:      3 [%]
GAL_COORDS:      217.44,-21.61 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       84.21,-36.81 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 25 Apr 20 00:38:36 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     967774,   Seg_Num: 0
GRB_RA:           85.2198d {+05h 40m 52.75s} (J2000),
                  85.4532d {+05h 41m 48.75s} (current),
                  84.6456d {+05h 38m 34.94s} (1950)
GRB_DEC:         -13.4352d {-13d 26' 06.7"} (J2000),
                 -13.4260d {-13d 25' 33.6"} (current),
                 -13.4598d {-13d 27' 35.2"} (1950)
GRB_ERROR:       2.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  18964 TJD;   116 DOY;   20/04/25
IMG_START_TIME:  1222.00 SOD {00:20:22.00} UT,   240.2 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        32.99d {+02h 11m 58s}  +13.28d {+13d 16' 51"}
SUN_DIST:         58.44 [deg]   Sun_angle= -3.5 [hr] (East of Sun)
MOON_POSTN:       55.03d {+03h 40m 07s}  +16.62d {+16d 37' 25"}
MOON_DIST:        42.50 [deg]
MOON_ILLUM:      3 [%]
GAL_COORDS:      217.40,-21.61 [deg] galactic lon,lat of the burst
ECL_COORDS:       84.19,-36.78 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.11% < P(seren) < 0.58%.

GCN Circular #27638
M. G. Bernardini (INAF-OAB), P. D'Avanzo (INAF-OAB), J.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (PSU), S. Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), M. J. Moss (GWU), D. M. Palmer (LANL), T. Sbarrato (INAF-OAB) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 00:16:21 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 200425A (trigger=967774). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 85.241, -13.459 which is
```
   RA(J2000) = 05h 40m 58s
   Dec(J2000) = -13d 27' 31"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The immediately-available BAT light curve data only extends to T+8s, at which time the GRB was still active with a multi-peaked structure. The peak count rate up to that time was ~1000 counts/sec (15-350 keV), at ~3 sec after the trigger.
The XRT began observing the field at 00:17:52.2 UT, 90.5 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 85.2198, -13.4352 which is equivalent to:
```
   RA(J2000)  = 05h 40m 52.76s
   Dec(J2000) = -13d 26' 06.8"
```
with an uncertainty of 2.9 arcseconds (radius, 90% containment). This location is 113 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 1.59 x 10^21 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 93 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.16.
Burst Advocate for this burst is M. G. Bernardini (grazia.bernardini AT brera.inaf.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)
GCN Circular #27639
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 3121 s of XRT Photon Counting mode data and 7 UVOT images for GRB 200425A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 85.21950, -13.43511 which is equivalent to:
```
RA (J2000): 05h 40m 52.68s
Dec (J2000): -13d 26' 06.4"
```
with an uncertainty of 1.6 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #27641
V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), J. D. Gropp (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB) and M.G. Bernardini report on behalf of the Swift-XRT team:
We have analysed 7.7 ks of XRT data for GRB 200425A (Bernardini et al. GCN Circ. 27638), from 78 s to 34.8 ks after the BAT trigger. The data comprise 145 s in Windowed Timing (WT) mode (the first 6 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 27639).
The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=2.5 (+1.3, -0.8). At T+105 s the decay flattens to an alpha of -1.5 (+0.0, -0.5). The light curve breaks again at T+125 s to a decay with alpha=2.78 (+0.39, -0.30), before a final break at T+268 s s after which the decay index is 1.13 (+/-0.06).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.11 (+0.17, -0.16). The best-fitting absorption column is 5.8 (+1.0, -0.9) x 10^21 cm^-2, in excess of the Galactic value of 1.6 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.02 (+0.26, -0.25) and a best-fitting absorption column of 7.2 (+2.1, -1.8) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.4 x 10^-11 (7.8 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     7.2 (+2.1, -1.8) x 10^21 cm^-2
Galactic foreground: 1.6 x 10^21 cm^-2
Excess significance: 5.2 sigma
Photon index:	     2.02 (+0.26, -0.25)
```
If the light curve continues to decay with a power-law decay index of 1.13, the count rate at T+24 hours will be 2.8 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x 10^-13 (2.2 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00967774.
This circular is an official product of the Swift-XRT team.
GCN Circular #27643
N. P. M. Kuin (UCL-MSSL) and M. G. Bernardini (INAF-OAB) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 200425A 94 s after the BAT trigger (Bernardini et al., GCN Circ. 27638). No optical afterglow consistent with the XRT position (Bernardini et al. GCN Circ. 27638)is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            94          244          147         >20.7
u_FC               253          503          246         >19.9
white               94          728          186         >20.5
v                  585          778           39         >18.6
b                  510          704           39         >19.1
u                  253          679          265         >19.9
w1                 635          827           39         >18.4
m2                 610          802           39         >18.9
w2                 560          753           39         >18.7
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.16 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #27645
V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 200425A ( M. G. Bernardini et al., GCN 27638) errorbox 60241 sec after notice time and 60296 sec after trigger time at 2020-04-25 17:01:17 UT, with upper limit up to 19.7 mag. Observations started at twilight. The observations began at zenith distance = 45 deg. The sun altitude is -12.2 deg.
The galactic latitude b = -21 deg., longitude l = 218 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1343952
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________


   60386 |         MASTER-SAAO |   C |   180 | 19.2 |        
   60434 |         MASTER-SAAO |   C |   180 | 19.2 |        
   60666 |         MASTER-SAAO |   C |   180 | 19.7 |        
   60713 |         MASTER-SAAO |   C |   180 | 19.7 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #27646
R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:
We observed Swift GRB 200425A (Bernardini et al., GCN 27638) with the LCO 1-m Sinistro instrument at the Siding Spring Observatory, Australia site, on April 25, from 08:26 to 09:07 UT (corresponding to 8.17 to 8.85 hours from the GRB trigger time) with the Bessel I and R filters.
We performed a series of 5x240s exposures in R and I. We do not detect any fading sources in the individual frames (or in stacked images) in the Enhanced Swift-XRT position region (Beardmore et al., GCN 27639). Using the USNO-B.1 catalog as reference, we obtain the following 3-sigma upper limits:
R > 22.45
I > 21.96
These magnitudes are not corrected for galactic extinction.
R.S. is funded by NSF AST grant #1831682
GCN Circular #27650
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), M. G. Bernardini (INAF-OAB), J. R. Cummings (CPI), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 200425A (trigger #967774) (Bernardini et al., GCN Circ. 27638). The BAT ground-calculated position is RA, Dec = 85.217, -13.399 deg which is
```
   RA(J2000)  =  05h 40m 52.2s
   Dec(J2000) = -13d 23' 58.1"
```
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%.
The mask-weighted light curve shows a weak pulse that starts at ~T-10 s, peaks at ~T+3 s, and ends at ~T+10 s. In addition, there is some weak emission that starts at ~T-50 s and lasts till ~T+60 s. T90 (15-350 keV) is 81.0 +- 21.7 sec (estimated error including systematics).
The time-averaged spectrum from T-47.59 to T+58.41 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.30 +- 0.21. The fluence in the 15-150 keV band is 1.2 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+2.41 sec in the 15-150 keV band is 0.7 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/967774/BA/

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Jochen Greiner, last update: 27-Apr-2020 [Disclaimer]